scholarly journals An SVEICRD model for assessing the impact of the lock-down intervention and vaccination strategies on the spread of COVID-19

2021 ◽  
Author(s):  
Idil Aydin ◽  
Aysun Bozanta ◽  
Mucahit Cevik ◽  
Ayse Basar
Keyword(s):  
Numerical Study ◽  
Vaccination Strategy ◽  
Alternative Strategies ◽  
Vaccination Strategies ◽  
The Uk ◽  
Fourth Wave ◽  
The Impact ◽  
Death Cases

In this research, we aim to forecast the trajectory of the COVID-19 pandemic in terms of the number of exposed, infected, vaccinated, hospitalized, recovered, and dead people, and observe the effects of different vaccination strategies on the spread of the COVID-19. We simulate the ongoing trajectory of the outbreak in three countries, namely, Canada, the UK, and Israel using the susceptible - vaccinated - exposed - infected - critical - recovered - dead (SVEICRD) model. We consider two vaccination strategies and investigate their effects on the number of exposed and death cases. We perform an extensive numerical study to assess the implications of different strategies and spread scenarios. Our findings confirm that the fourth wave has begun in all three countries, and already reached its peak. We observe that starting second dose vaccination as early as possible is the most effective in mitigating the spread of COVID-19, although it does require more vaccination supply than the alternative strategies. Our results show that the SVEICRD model successfully forecasts the changing number of people in each compartment and the vaccination strategy significantly impacts the trajectory of the outbreak.

scholarly journals Modelling the impact of reopening schools in early 2021 in the presence of the new SARS-CoV-2 variant and with roll-out of vaccination against COVID-19

2021 ◽  
Author(s):  
Jasmina Panovska-Griffiths ◽  
Robyn Stuart ◽  
Cliff Kerr ◽  
Katherine Rosenfeld ◽  
Dina Mistry ◽  
...  
Keyword(s):  
Secondary Schools ◽  
Primary Schools ◽  
Vaccination Strategy ◽  
Transmission Blocking ◽  
Social Distancing ◽  
New Variant ◽  
The Uk ◽  
And Control ◽  
The Impact ◽  
Roll Out

Abstract Background Following the resurgence of the COVID-19 epidemic in the UK in late 2020 and the emergence of the new variant of the SARS-CoV-2 virus, B.1.1.7, a third national lockdown was imposed from January 5, 2021. Following the decline of COVID-19 cases over the remainder of January 2021, it is important to assess the conditions under which reopening schools from early March is likely to lead to resurgence of the epidemic. This study models the impact of a partial national lockdown with social distancing measures enacted in communities and workplaces under different strategies of reopening schools from March 8, 2021 and compares it to the impact of continual full national lockdown remaining until April 19, 2021. Methods We used our previously published model, Covasim, to model the emergence of B.1.1.7 over September 1, 2020 to January 31, 2021. We extended the model to incorporate the impacts of the roll-out of a two-dose vaccine against COVID-19, assuming 200,000 daily doses of the vaccine in people 75 years or older with vaccination that offers 95% reduction in disease acquisition and 10% reduction of transmission blocking. We used the model, calibrated until January 25, 2021, to simulate the impact of a full national lockdown (FNL) with schools closed until April 19, 2021 versus four different partial national lockdown (PNL) scenarios with different elements of schooling open: 1) staggered PNL with primary schools and exam-entry years (years 11 and 13) returning on March 8, 2021 and the rest of the schools years on March 15, 2020; 2) full-return PNL with both primary and secondary schools returning on March 8, 2021; 3) primary-only PNL with primary schools and exam critical years (Y11 and Y13) going back only on March 8, 2021 with the rest of the secondary schools back on April 19, 2021 and 4) part-Rota PNL with both primary and secondary schools returning on March 8, 2021 with primary schools remaining open continuously but secondary schools on a two-weekly rota-system with years alternating between a fortnight of face-to-face and remote learning until April 19, 2021. Across all scenarios, we projected the number of new daily cases, cumulative deaths and effective reproduction number R until April 30, 2020. Results Our calibration across different scenarios is consistent with the new variant B.1.1.7 being around 60% more transmissible. Strict social distancing measures, i.e. national lockdowns, are required to contain the spread of the virus and control the hospitalisations and deaths during January and February 2021. The national lockdown will reduce the number of cases by early March levels similar to those seen in October with R also falling and remaining below 1 during the lockdown. Infections start to increase when schools open but if other parts of society remain closed this resurgence is not sufficient to bring R above 1. Reopening primary schools and exam critical years only or having primary schools open continuously with secondary schools on rotas will lead to lower increases in cases and R than if all schools open. Under the current vaccination assumptions and across the set of scenarios considered, R would increase above 1 if society reopens simultaneously, simulated here from April 19, 2021.Findings Our findings suggest that stringent measures are necessary to mitigate the increase in cases and bring R below 1 over January and February 2021. It is plausible that a PNL with schools partially open from March 8, 2021 and the rest of the society remaining closed until April 19, 2021 may keep R below 1, with some increase evident in infections compared to continual FNL until April 19, 2021. Reopening society in mid-April, with the vaccination strategy we model, could push R above 1 and induce a surge in infections, but the effect of vaccination may be able to control this in future depending on the transmission blocking properties of the vaccines.

scholarly journals Preventing the Risk of Hospitalization for Respiratory Complications of Influenza among the Elderly: Is There a Better Influenza Vaccination Strategy? A Retrospective Population Study

Vaccines ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 344
Author(s):  
Silvia Cocchio ◽  
Tolinda Gallo ◽  
Stefania Del Zotto ◽  
Elena Clagnan ◽  
Andrea Iob ◽  
...  
Keyword(s):  
Influenza Vaccination ◽  
Vaccination Strategy ◽  
The Elderly ◽  
Protective Role ◽  
The Body ◽  
Health Concern ◽  
Respiratory Complications ◽  
Effective Prevention ◽  
Vaccination Strategies ◽  
The Impact

Influenza and its complications are an important public health concern, and vaccination remains the most effective prevention measure. However, the efficacy of vaccination depends on several variables, including the type of strategy adopted. The goal of this study was to assess the impact of different influenza vaccination strategies in preventing hospitalizations for influenza and its related respiratory complications. A retrospective cohort study was conducted on data routinely collected by the health services for six consecutive influenza seasons, considering the population aged 65 years or more at the time of their vaccination and living in northeastern Italy. Our analysis concerns 987,266 individuals vaccinated against influenza during the study period. The sample was a mean 78.0 ± 7.7 years old, and 5681 individuals (0.58%) were hospitalized for potentially influenza-related reasons. The hospitalization rate tended to increase over the years, not-significantly peaking in the 2016–2017 flu season (0.8%). Our main findings revealed that hospitalizations related to seasonal respiratory diseases were reduced as the use of the enhanced vaccine increased (R2 = 0.5234; p < 0.001). Multivariate analysis confirmed the significantly greater protective role of the enhanced vaccine over the conventional vaccination strategy, with adjusted Odds Ratio (adj OR) = 0.62 (95% CI: 0.59–0.66). A prior flu vaccination also had a protective role (adj OR: 0.752 (95% CI: 0.70–0.81)). Age, male sex, and H3N2 mismatch were directly associated with a higher risk of hospitalization for pneumonia. In the second part of our analysis, comparing MF59-adjuvanted trivalent inactivated vaccine (MF59-TIV) with conventional vaccines, we considered 479,397 individuals, of which 3176 (0.66%) were admitted to a hospital. The results show that using the former vaccine reduced the risk of hospitalization by 33% (adj OR: 0.67 (95% CI: 0.59–0.75)). This study contributes to the body of evidence of a greater efficacy of enhanced vaccines, and MF59-adjuvanted TIV in particular, over conventional vaccination strategies in the elderly.

Modelling the impact of one-dose vs. two-dose vaccination regimens on the epidemiology of varicella zoster virus in Australia

2009 ◽  
Vol 138 (4) ◽  
pp. 457-468 ◽  
Author(s):  
Z. GAO ◽  
H. F. GIDDING ◽  
J. G. WOOD ◽  
C. R. MacINTYRE
Keyword(s):  
Mathematical Model ◽  
Varicella Zoster Virus ◽  
Vaccination Strategy ◽  
Vaccination Schedule ◽  
Varicella Zoster ◽  
Dose Strategy ◽  
Vaccination Strategies ◽  
Age Of Infection ◽  
The Impact

SUMMARYWe examined the impact of one-dose vs. two-dose vaccination strategies on the epidemiology of varicella zoster virus (VZV) in Australia, using a mathematical model. Strategies were assessed in terms of varicella (natural and breakthrough) and zoster incidence, morbidity, average age of infection and vaccine effectiveness (VE). Our modelling results suggest that compared to a one-dose vaccination strategy (Australia's current vaccination schedule), a two-dose strategy is expected to not only produce less natural varicella cases (5% vs. 13% of pre-vaccination state, respectively) but also considerably fewer breakthrough varicella cases (only 11·4% of one-dose strategy). Therefore a two-dose infant vaccination programme would be a better long-term strategy for Australia.

scholarly journals The transmission dynamics of hepatitis B in the UK: a mathematical model for evaluating costs and effectiveness of immunization programmes

1996 ◽  
Vol 116 (1) ◽  
pp. 71-89 ◽  
Author(s):  
J. R. Williams ◽  
D. J. Nokes ◽  
G. F. Medley ◽  
R. M. Anderson
Keyword(s):  
Mathematical Model ◽  
Hepatitis B ◽  
Vaccine Coverage ◽  
Vaccine Dose ◽  
Transmission Dynamics ◽  
Costs And Benefits ◽  
Vaccination Strategies ◽  
The Uk ◽  
The Impact ◽  
Immunization Programmes

SummaryComplex hepatitis B (HBV) epidemiology makes it difficult to evaluate and compare effectiveness of different immunization policies. A method for doing so is presented using a mathematical model of HBV transmission dynamics which can represent universal infant and adolescent vaccination strategies and those targeted at genito-urinary (GU) clinic attenders and infants born to infectious mothers. Model structure, epidemiological underpinning, and parameterization, are described. Data from the UK National Survey of Sexual Attitudes and Lifestyles is used to define patterns of sexual activity and GU clinic attendance; data deficiencies are discussed, in particular that of UK seroprevalence of HBV markers stratified by age, sex, and risk factors. General model predictions of endemic HBV marker prevalence in homosexual and heterosexual populations seem consistent with published UK data. The simulations exhibit non-linearities in the impact of different vaccination strategies. Estimated number of carriers prevented per vaccine dose for each strategy provides a measure of costs and benefits, varying temporally over the course of a programme, and with level of vaccine coverage. Screening before vaccination markedly increases payback per dose in homosexuals but not in heterosexuals; mass infant vaccination gives the poorest effectiveness ratio and vaccination of infants after antenatal screening the best; in general, increasing vaccine coverage yields lower pay-back per dose. The model provides a useful framework for evaluating costs and benefits of immunization programmes, but for precise quantitative comparison more UK epidemiological data is urgently needed.

scholarly journals The potential impact of delta variant of SARS-CoV-2 in the context of limited vaccination coverage and increasing social mixing in Bogotá, Colombia

2021 ◽  
Author(s):  
Guido España ◽  
Zulma M Cucunubá ◽  
Juliana Cuervo-Rojas ◽  
Hernando Díaz ◽  
Manuel González-Mayorga ◽  
...  
Keyword(s):  
Vaccination Coverage ◽  
Social Contact ◽  
Vaccination Strategy ◽  
Major Effect ◽  
High Coverage ◽  
Social Mixing ◽  
Potential Impact ◽  
Fourth Wave ◽  
The Impact ◽  
The City

Background: More than 122,000 COVID-19 associated deaths have been reported in Colombia and about 27,000 in the city of Bogotá by the first week of August, with vaccination coverage in the city at 30% for complete schemes and at 37% for partial vaccination. As the incidence of cases currently decreases, questions remain about the potential impact of the delta variant already present in the city. Methods: We used an agent-based model calibrated to data on age-structured deaths and dominance of variants in Bogotá. We used efficacy data for the portfolio of vaccines available, including known changes for SARS-CoV-2 variants. We modelled scenarios of early and delayed introduction of the delta variant in the city along with changes in mobility and social contact, and vaccine strategies over the next months. Findings: We estimate that by mid July, vaccination may have already prevented 17,800 (95% CrI: 16,000 - 19,000) deaths in Bogotá. The delta variant could become dominant and lead to a fourth wave later in the year, but its timing will depend on the date of introduction, social mixing patterns, and vaccination strategy. In all scenarios, higher social mixing is associated with a fourth wave of considerable magnitude. If an early delta introduction occurred (dominance by mid July), a new wave may occur in August/September and in such case, age prioritization of vaccination and second dose not postponed are more important. However, if introduction occurred one or two months later (dominance by mid August/September) the age-prioritization is less relevant but maintaining the dose scheme without postponement is more important. In all scenarios we found that increasing the vaccination rate from the current average of 50,000/day to 100,000/day reduces the impact of a fourth wave due to the delta variant. Conclusions: In Bogotá, the delta variant could still lead to a fourth wave, whose magnitude would depend on its introduction time and the level of social mixing. Its impact can be mitigated by increasing vaccination rates to achieve high coverage quickly, with non-delayed second doses. We found that, at this point, suspending the age prioritization to achieve higher coverage with first doses does not seem to have a major effect on deaths and ICU demand. But, delaying the second dose may not be beneficial and may even increase the incidence of severe outcomes.

scholarly journals Assessing vaccination priorities for different ages and age-specific vaccination strategies of COVID-19 using an SEIR modelling approach

PLoS ONE ◽  
2021 ◽  
Vol 16 (12) ◽  
pp. e0261236
Author(s):  
Cong Yang ◽  
Yali Yang ◽  
Yang Li
Keyword(s):  
Young People ◽  
Reproduction Number ◽  
Vaccination Strategy ◽  
The Elderly ◽  
Seir Model ◽  
Global Epidemic ◽  
Vaccination Strategies ◽  
The Past ◽  
The Impact ◽  
Modelling Approach

In the past year, the global epidemic situation is still not optimistic, showing a trend of continuous expansion. With the research and application of vaccines, there is an urgent need to develop some optimal vaccination strategies. How to make a reasonable vaccination strategy to determine the priority of vaccination under the limited vaccine resources to control the epidemic and reduce human casualties? We build a dynamic model with vaccination which is extended the classical SEIR model. By fitting the epidemic data of three countries—China, Brazil, Indonesia, we have evaluated age-specific vaccination strategy for the number of infections and deaths. Furthermore, we have evaluated the impact of age-specific vaccination strategies on the number of the basic reproduction number. At last, we also have evaluated the different age structure of the vaccination priority. It shows that giving priority to vaccination of young people can control the number of infections, while giving priority to vaccination of the elderly can greatly reduce the number of deaths in most cases. Furthermore, we have found that young people should be mainly vaccinated to reduce the number of infections. When the emphasis is on reducing the number of deaths, it is important to focus vaccination on the elderly. Simulations suggest that appropriate age-specific vaccination strategies can effectively control the epidemic, both in terms of the number of infections and deaths.

scholarly journals Vaccination strategies against COVID-19 and the diffusion of anti-vaccination views

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rafael Prieto Curiel ◽  
Humberto González Ramírez
Keyword(s):  
Diffusion Model ◽  
Large Population ◽  
Vaccination Strategy ◽  
Small World ◽  
Years Of Life Lost ◽  
Scale Free ◽  
Vaccination Strategies ◽  
Network Topologies ◽  
Network Disruptions ◽  
The Impact

AbstractMisinformation is usually adjusted to fit distinct narratives and propagates rapidly through social networks. False beliefs, once adopted, are rarely corrected. Amidst the COVID-19 crisis, pandemic-deniers and people who oppose wearing face masks or quarantine have already been a substantial aspect of the development of the pandemic. With the vaccine for COVID-19, different anti-vaccine narratives are being created and are probably being adopted by large population groups with critical consequences. Assuming full adherence to vaccine administration, we use a diffusion model to analyse epidemic spreading and the impact of different vaccination strategies, measured with the average years of life lost, in three network topologies (a proximity, a scale-free and a small-world network). Then, using a similar diffusion model, we consider the spread of anti-vaccine views in the network, which are adopted based on a persuasiveness parameter of anti-vaccine views. Results show that even if anti-vaccine narratives have a small persuasiveness, a large part of the population will be rapidly exposed to them. Assuming that all individuals are equally likely to adopt anti-vaccine views after being exposed, more central nodes in the network, which are more exposed to these views, are more likely to adopt them. Comparing years of life lost, anti-vaccine views could have a significant cost not only on those who share them, since the core social benefits of a limited vaccination strategy (reduction of susceptible hosts, network disruptions and slowing the spread of the disease) are substantially shortened.

scholarly journals Modelling the impact of reopening schools in early 2021 in the presence of the new SARS-CoV-2 variant and with roll-out of vaccination against COVID-19

2021 ◽  
Author(s):  
J. Panovska-Griffiths ◽  
R.M. Stuart ◽  
C.C. Kerr ◽  
K. Rosenfield ◽  
D. Mistry ◽  
...  
Keyword(s):  
Secondary Schools ◽  
Primary Schools ◽  
Vaccination Strategy ◽  
Transmission Blocking ◽  
Social Distancing ◽  
New Variant ◽  
The Uk ◽  
And Control ◽  
The Impact ◽  
Roll Out

BackgroundFollowing the resurgence of the COVID-19 epidemic in the UK in late 2020 and the emergence of the new variant of the SARS-CoV-2 virus, B.1.1.7, a third national lockdown was imposed from January 5, 2021. Following the decline of COVID-19 cases over the remainder of January 2021, it is important to assess the conditions under which reopening schools from early March is likely to lead to resurgence of the epidemic. This study models the impact of a partial national lockdown with social distancing measures enacted in communities and workplaces under different strategies of reopening schools from March 8, 2021 and compares it to the impact of continual full national lockdown remaining until April 19, 2021.MethodsWe used our previously published model, Covasim, to model the emergence of B.1.1.7 over September 1, 2020 to January 31, 2021. We extended the model to incorporate the impacts of the roll-out of a two-dose vaccine against COVID-19, assuming 200,000 daily doses of the vaccine in people 75 years or older with vaccination that offers 95% reduction in disease acquisition and 10% reduction of transmission blocking. We used the model, calibrated until January 25, 2021, to simulate the impact of a full national lockdown (FNL) with schools closed until April 19, 2021 versus four different partial national lockdown (PNL) scenarios with different elements of schooling open: 1) staggered PNL with primary schools and exam-entry years (years 11 and 13) returning on March 8, 2021 and the rest of the schools years on March 15, 2020; 2) full-return PNL with both primary and secondary schools returning on March 8, 2021; 3) primary-only PNL with primary schools and exam critical years (Y11 and Y13) going back only on March 8, 2021 with the rest of the secondary schools back on April 19, 2021 and 4) part-Rota PNL with both primary and secondary schools returning on March 8, 2021 with primary schools remaining open continuously but secondary schools on a two-weekly rota-system with years alternating between a fortnight of face-to-face and remote learning until April 19, 2021. Across all scenarios, we projected the number of new daily cases, cumulative deaths and effective reproduction number R until April 30, 2020.ResultsOur calibration across different scenarios is consistent with the new variant B.1.1.7 being around 60% more transmissible. Strict social distancing measures, i.e. national lockdowns, are required to contain the spread of the virus and control the hospitalisations and deaths during January and February 2021. The national lockdown will reduce the number of cases by early March levels similar to those seen in October with R also falling and remaining below 1 during the lockdown. Infections start to increase when schools open but if other parts of society remain closed this resurgence is not sufficient to bring R above 1. Reopening primary schools and exam critical years only or having primary schools open continuously with secondary schools on rotas will lead to lower increases in cases and R than if all schools open. Under the current vaccination assumptions and across the set of scenarios considered, R would increase above 1 if society reopens simultaneously, simulated here from April 19, 2021.FindingsOur findings suggest that stringent measures are necessary to mitigate the increase in cases and bring R below 1 over January and February 2021. It is plausible that a PNL with schools partially open from March 8, 2021 and the rest of the society remaining closed until April 19, 2021 may keep R below 1, with some increase evident in infections compared to continual FNL until April 19, 2021. Reopening society in mid-April, with the vaccination strategy we model, could push R above 1 and induce a surge in infections, but the effect of vaccination may be able to control this in future depending on the transmission blocking properties of the vaccines.

scholarly journals Vaccination strategies to control Ebola epidemics in the context of variable household inaccessibility levels

2019 ◽  
Author(s):  
G. Chowell ◽  
A. Tariq ◽  
M. Kiskowski
Keyword(s):  
Vaccination Strategy ◽  
Qualitative Change ◽  
Health Interventions ◽  
Transmission Model ◽  
Individual Level ◽  
Vaccination Strategies ◽  
Ring Vaccination ◽  
Low Levels ◽  
The Impact ◽  
Close Contacts

AbstractDespite a very effective vaccine, active conflict and community distrust during the ongoing DRC Ebola epidemic are undermining control efforts, including a ring vaccination strategy that requires the prompt immunization of close contacts of infected individuals. However, in April 2019, it was reported 20% or more of close contacts cannot be reached or refuse vaccination [1], and it is predicted that the ring vaccination strategy would not be effective with such a high level of inaccessibility [2]. The vaccination strategy is now incorporating a “third ring” community-level vaccination that targets members of communities even if they are not known contacts of Ebola cases. To assess the impact of vaccination strategies for controlling Ebola epidemics in the context of variable levels of community accessibility, we employed an individual-level stochastic transmission model that incorporates four sources of heterogeneity: a proportion of the population is inaccessible for contact tracing and vaccination due to lack of confidence in interventions or geographic inaccessibility, two levels of population mixing resembling household and community transmission, two types of vaccine doses with different time periods until immunity, and transmission rates that depend on spatial distance. Our results indicate that a ring vaccination strategy alone would not be effective for containing the epidemic in the context of significant delays to vaccinating contacts even for low levels of household inaccessibility and affirm the positive impact of a supplemental community vaccination strategy. Our key results are that as levels of inaccessibility increase, there is a qualitative change in the effectiveness of the vaccination strategy. For higher levels of vaccine access, the probability that the epidemic will end steadily increases over time, even if probabilities are lower than they would be otherwise with full community participation. For levels of vaccine access that are too low, however, the vaccination strategies are not expected to be successful in ending the epidemic even though they help lower incidence levels, which saves lives, and makes the epidemic easier to contain and reduces spread to other communities. This qualitative change occurs for both types of vaccination strategies: ring vaccination is effective for containing an outbreak until the levels of inaccessibility exceeds approximately 10% in the context of significant delays to vaccinating contacts, a combined ring and community vaccination strategy is effective until the levels of inaccessibility exceeds approximately 50%. More broadly, our results underscore the need to enhance community engagement to public health interventions in order to enhance the effectiveness of control interventions to ensure outbreak containment.Author summaryIn the context of the ongoing Ebola epidemic in DRC, active conflict and community distrust are undermining control efforts, including vaccination strategies. In this paper, we employed an individual-level stochastic structured transmission model to assess the impact of vaccination strategies on epidemic control in the context of variable levels of household inaccessibility. We found that a ring vaccination strategy of close contacts would not be effective for containing the epidemic in the context of significant delays to vaccinating contacts even for low levels of household inaccessibility and evaluate the impact of a supplemental community vaccination strategy. For lower levels of inaccessibility, the probability of epidemic containment increases over time. For higher levels of inaccessibility, even the combined ring and community vaccination strategies are not expected to contain the epidemic even though they help lower incidence levels, which saves lives, makes the epidemic easier to contain and reduces spread to other communities. We found that ring vaccination is effective for containing an outbreak until the levels of inaccessibility exceeds approximately 10%, a combined ring and community vaccination strategy is effective until the levels of inaccessibility exceeds approximately 50%. Our findings underscore the need to enhance community engagement to public health interventions.

scholarly journals Clinical and economic impact of universal varicella vaccination in Norway: A modeling study

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0254080
Author(s):  
Manjiri Pawaskar ◽  
Colleen Burgess ◽  
Mathew Pillsbury ◽  
Torbjørn Wisløff ◽  
Elmira Flem
Keyword(s):  
Cost Saving ◽  
Varicella Vaccine ◽  
Vaccination Strategy ◽  
Quadrivalent Vaccine ◽  
Transmission Model ◽  
Varicella Vaccination ◽  
Vaccination Strategies ◽  
Dynamic Transmission Model ◽  
Life Years ◽  
The Impact

Background Norway has not implemented universal varicella vaccination, despite the considerable clinical and economic burden of varicella disease. Methods An existing dynamic transmission model of varicella infection was calibrated to age-specific seroprevalence rates in Norway. Six two-dose vaccination strategies were considered, consisting of combinations of two formulations each of a monovalent varicella vaccine (Varivax® or Varilrix®) and a quadrivalent vaccine against measles-mumps-rubella-varicella (ProQuad® or PriorixTetra®), with the first dose given with a monovalent vaccine at age 15 months, and the second dose with either a monovalent or quadrivalent vaccine at either 18 months, 7 or 11 years. Costs were considered from the perspectives of both the health care system and society. Quality-adjusted life-years saved and incremental cost-effectiveness ratios relative to no vaccination were calculated. A one-way sensitivity analysis was conducted to assess the impact of vaccine efficacy, price, the costs of a lost workday and of inpatient and outpatient care, vaccination coverage, and discount rate. Results In the absence of varicella vaccination, the annual incidence of natural varicella is estimated to be 1,359 per 100,000 population, and the cumulative numbers of varicella outpatient cases, hospitalizations, and deaths over 50 years are projected to be 1.81 million, 10,161, and 61, respectively. Universal varicella vaccination is projected to reduce the natural varicella incidence rate to 48–59 per 100,000 population, depending on the vaccination strategy, and to reduce varicella outpatient cases, hospitalizations, and deaths by 75–85%, 67–79%, and 75–79%, respectively. All strategies were cost-saving, with the most cost-saving as two doses of Varivax® at 15 months and 7 years (payer perspective) and two doses of Varivax® at 15 months and 18 months (societal perspective). Conclusions All modeled two-dose varicella vaccination strategies are projected to lead to substantial reductions in varicella disease and to be cost saving compared to no vaccination in Norway.

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